Kuroshio Biosphere Vol. 3, Mar. 2007, pp. 1-16 + 7 pls.

PRELIMINARY SURVEY OF ZOOXANTHELLATE ZOANTHID DIVERSITY (HEXACORALLIA: ) FROM SOUTHERN SHIKOKU, JAPAN

by

James Davis REIMER1, 2

Abstract

Zooxanthellate members of the order Zoantharia (: Hexacorallia) previously reported from Japan consist of the genera Zoanthus and Isaurus in the family as well as the genus Palythoa in the family Sphenopidae. In particular, Zoanthus and Palythoa are common in shallow tropical and sub-tropical waters from the southern limits of Japan in Okinawa to their northern limits in the Izu Islands (Miyakejima Island). Previous studies have documented the occurrence of zooxanthellate zoanthids in Okinawa, the Nansei Islands, Kyushu, mid-Honshu (Wakayama), and the Izu Islands, but until now no formal survey of zoanthids occurring in the waters of Shikoku has been conducted. The area surveyed in this study was divided into two regions: zooxanthellate zoanthid diversity was higher (8 species) along the southern Pacific Coast region of Kochi, and lower in waters of the Bungo Strait region (5 species). The majority of observed species listed here were found below the extreme low tide line to depths of approximately 5 m. Zoanthus and Palythoa were found in most sites surveyed, while Isaurus was limited to sites on the Pacific coast. Zooxanthellate zoanthids in southern Shikoku are most abundant in shallow hard substrate marine habitats with a well-developed coastal terrace, and consistent high amounts of wave activity, current, and light levels.

Introduction

In recent years, research has begun to investigate the diversity of zooxanthellate zoanthids (Anthozoa: Hexacorallia: Zoantharia) from Japanese waters. Distribution of the genera Zoanthus, Isaurus (Family Zoanthidae) and Palythoa (Sphenopidae) roughly follows the course of the Kuroshio Current, which brings warm tropical waters from Okinawa and the east coast of Taiwan to high latitudes of the Pacific coast of Japan (Fig. 1a). While the genus Isaurus has only been previously reported from a few sites in Japan (including the Danjo Islands, Tatsukushi, and Otsuki – Nishidomari-Matsubae; F. Iwase, personal communication; also see Fig. 1b), there are numerous documented samples of Zoanthus and Palythoa spp. from Okinawa, the Nansei Islands, Kyushu, mid-Honshu, and the Izu Islands (see Uchida 2001; Reimer et al. 2006a; Reimer et al. 2006d; Fig. 1a). However, until now there has been no investigation into the diversity of zooxanthellate zoanthids from the waters of Shikoku, representing a critical gap in the reported distributions of these cnidarians in Japan.

1. Biological Institute on Kuroshio, 560 Nishidomari, Otsuki, Kochi 788-0333, Japan 2. Marine Biology and Ecology Research Program, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan. e-mail: [email protected] 2 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

Fig. 1. a) Map of previous zooxanthellate zoanthid sampling sites in Japan with area of this study. Black closed circles represent areas where zooxanthellate zoanthids have previously been found, and crosses areas that were previously investigated but no zooxanthellate zoanthids found; b) map of sampling sites investigated in this study. The dotted line represents the border between the two regions of this study. Numbered sites correspond to site numbers as given in Table 2. REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 3

The area investigated in this study (from Cape Ashizuri, Kochi to Yura Peninsula, Ehime; see Fig. 1b) can be geographically divided into two regions. The Pacific Coast region (Cape Ashizuri to Kashiwajima) features frequent waves and has a well-developed coastal terrace, while the region from Kashiwajima to Yura Peninsula is somewhat more protected from open ocean waves, and has steep rocky cliffs that extend underwater (Iwase 2004) (Table 1). Both regions are strongly influenced by the Kuroshio Current. Additionally, both regions have several marine parks and Marine Protected Areas (MPAs) (Iwase 2004), with detailed species lists for many groups of marine organisms. Unfortunately, few if any zoanthid species appear on such lists despite their presumed presence in the parks and MPAs. Here, in order to provide detailed information on zooxanthellate zoanthid diversity and distribution in Shikoku, we have conducted surveys of numerous locations in southern Kochi and western Ehime prefectures (Fig. 1b). We provide a species list, a morphological dichotomous key for all zooxanthellate zoanthids observed, and also discuss some of their ecological characteristics.

Table 1. Description of environment and fauna in the two regions of southern Shikoku investigated in this study.

Maximum Minimum Commonly Average ocean Region General description ocean ocean observed temperature1 temperature1 temperature1 benthos2

Directly on open ocean, Acropora spp., Pacific strong Kuroshio influence, Pavona spp., 28.62 °C 14.72 °C 21.74 ± 3.67 °C Coast ocean terraces, points and other hermatypic bays interspersed corals. More sheltered from open ocean, strong Kuroshio Acropora spp., Bungo influence, steep complex 29.12 °C 16.15 °C 22.01 ± 3.46 °C Tubastraea spp., Strait cliffs that continue into Alcyonacea ocean 1Temperature data from HOBO Water Temp Pro (Onset Com puter Corporation, Bourne, MA, USA) sensors recording at one hour intervals, for the period from March 29, 2005 to March 15, 2006 (n=8348). Pacific Coast region sensor placed at Nishidomari site (depth = 6 m), Bungo Strait region sensor at Tachinbanaura site (depth = 10 m). 2From Iwase (2004).

Materials and methods

Samples: Zooxanthellate zoanthid species and their relative abundance were noted at 23 locations (Fig. 1, Table 2) in southern Shikoku between January and October 2006 by SCUBA and/or snorkeling. Other data recorded included depth and colony size. In situ photographs were taken to assist in further analyses (oral disk color, tentacle number, etc.) in the laboratory. Samples of each species were collected from all locations in Kochi Prefecture, and have been deposited in JDR’s zoanthid collection at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC; Yokosuka, Japan) or at the Biological Institute at Kuroshio (BIK; Otsuki, Japan). No samples were collected in Ehime Prefecture due to prefectural sampling restrictions, but it is hoped samples can be obtained in the future. Samples were preserved 4 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

X X X ★ ○ ○ ○ ○ ○ ○ ○ ◎ ○ ○ mutuki Palythoa

★ ◎ ◎ ◎ ◎ ○ ● ◎ ● ● ◎ ◎ ●● ●● Palythoa tuberculosa

1 1 X X X X X X X X X X ★ sp. B Isaurus

X X X X ★ ○ ◎ ○ ○ ◎ ○ ○ ○ Isaurus tuberculatus tuberculatus

X X X X X X X X X X X X X ★ ◎ kuroshio kuroshio Zoanthus Zoanthus

★ ◎ ◎ ● ◎ ○ ● ◎ ● ◎ ◎ ◎ ●● ●● Zoanthus vietnamensis vietnamensis

★ ◎ ◎ ● ◎ ○ ● ● ◎ ● ◎ ◎ ◎ ●● gigantus gigantus Zoanthus outhern Shikoku by location. location. by Shikoku outhern 3

★ ◎ ◎ ● ◎ ○ ● ◎ ○ ○ ◎ ○ ◎ ◎ Zoanthus sansibaricus Wave/ current current activity activity

ellae Zoantharia species in s in species ellae Zoantharia 2

Site type Site (with number 1 / site Shirigai-Matsubae Outside High High Outside Shirigai-Matsubae Oshirigai Bay Medium Medium Bay Oshirigai Odo North Outside High Odo South South Odo Outside High

Mizushima Outside High High High Outside Mizushima Omurabae Outside Tatsukushi-Bentenjima Outside Medium Medium Outside Tatsukushi-Bentenjima Obae Outside Medium Obae Outside Hozaki Outside High Hozaki Outside Nishidomari-Matsubae Outside Outside Nishidomari-Matsubae High Nishidomari Bay Medium Nishidomari Bay Nishidomari South Outside High Kashinoura-Bentenjima Outside Outside Kashinoura-Bentenjima High

of species in area) Region Pacific Coast (8 species) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Table 2. Abundanceof zooxanth 2. Table

REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 5

X X X X X X X X ○ mutuki Palythoa

X X X ★ ★ ◎ ◎ ○ ● ◎ ● ●● Palythoa tuberculosa

aves and more sheltered than “Bay”, X X X X X X X X X X sp. B Isaurus

X X X X X X X X X X Isaurus tuberculatus tuberculatus

X X X X X X X X X =single colony present, X=not present. X=not present. =single colony present, 1 kuroshio kuroshio Zoanthus Zoanthus ely protected from open ocean w =rare, ○

1 X X X X ◎ ◎ ◎ ● ●● ●● Zoanthus vietnamensis vietnamensis =uncommon, =uncommon,

◎

X X X X ◎ ◎ ◎ ● ◎ ● gigantus gigantus Zoanthus tially sheltered, Sheltered=larg 3 =common, =common, ●

X X X X X X ◎ ★ ● ★ ★ ◎ ● Zoanthus sansibaricus =abundant, =abundant, ●● Wave/ current current activity activity

2

Site type Site (with number 1 / site =species present in region. Abundance symbols: symbols: Abundance in region. =species present Site numbers correspond to site numbers in Figure 1b. in Figure correspond to site numbers Site numbers open ocean but par to open ocean, Bay=exposed Outside=exposed ★ 18. Tachibanaura Harbor Shirozaki 19. Harbor Low Sheltered 22. Kashima Low Sheltered Low of species in area) Region (5 species) Strait Bungo 14. Torinokubi Oura 15. Outside 17. Komo High Bay Medium Sheltered 21. Kurobae Medium Sheltered High 23. Yokoshima Yokoshima 23. Sheltered High 20. Jinoiso Jinoiso 20. Outside High 16. Futatsubae 16. Futatsubae Sheltered Medium Harbor=within breakwaters, no waves. no waves. breakwaters, Harbor=within 1 2 3 Table 2. continued continued 2. Table

6 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007 in 99.5 % ethanol at –30 °C for future DNA analyses (as in Reimer et al. 2004; 2006a; 2006c; etc.) or in 10 % formalin seawater for future morphological analyses (as in Ono et al. 2005). Regions and locations: The sampling area in southern Shikoku was divided into two regions (Pacific Coast and Bungo Strait) based on observed differences in environment and predominant benthos within region (see Iwase 2004) (Fig. 1b, Table 1). Each location within each region’s “ocean exposure” was classified as either “outside” (directly exposed to the open ocean), “bay” (somewhat sheltered from open ocean), “protected” (non-“bay” but sheltered from open ocean), or “harbor” (completely sheltered from open ocean). Additionally, wave and tidal current activity at each location was assessed by a combination of high wave lines onshore and local diving guide information combined with previous references into three categories (“high”, “medium”, or “low”). Species Identification: Species were identified in situ using previously reported morphological characteristics (Zoanthus – see Reimer et al. 2006a; Reimer et al. 2006b; Palythoa – see Reimer et al. 2006c; Isaurus – see Uchida 2001). In addition, some samples had their identities further confirmed by DNA sequencing (data to appear elsewhere). Species diversity analyses: After collection of samples and field data, zooxanthellate zoanthid species diversity was analyzed by comparing species numbers between regions between locations classified by ocean exposure classes (“outside” vs. all “sheltered” classes), and between locations classified by wave and current classes.

Results

A list of zooxanthellate zoanthid species by location is shown in Table 2, with representative in situ photographs of zooxanthellate zoanthid species in Fig. 2. Overall, Zoanthus vietnamensis Pax & Mueller and Palythoa tuberculosa Delage & Herouard were seen to be the most widely found zooxanthellate zoanthids (20/23 locations investigated), with Zoanthus kuroshio Reimer & Ono and an unidentified Isaurus species (designated Isaurus species B here) found at only one location each (Tables 2 & 3). No zooxanthellate zoanthids were found at two locations, both in the Bungo Strait region (Table 2).

Table 3. Frequency of occurrence of zooxanthellate zoanthid species at investigated sites in southern Shikoku. Pacific Coast region species diversity Pacific Coast region site Total site Bungo Strait region site occurrences (13 total occurrences (23 total Species occurrences (10 total sites) sites) sites) Zoanthus sansibaricus 13 4 17 Zoanthus gigantus 13 6 19 Zoanthus vietnamensis 13 7 20 Zoanthus kuroshio 1 0 1 Isaurus assymetricus 8 0 8 Isaurus sp. B 2 0 2 Palythoa tuberculosa 13 7 20 Palythoa mutuki 10 1 11 REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 7

13 sites were investigated along the Pacific Coast region (Fig. 1b, Table 2). At all sites Zoanthus sansibaricus Carlgren (Pl. 1), Zoanthus gigantus Reimer and Tsukahara (Pl. 2), Zoanthus vietnamensis sensu Uchida (2001) (Pl. 3 A-C), and Palythoa tuberculosa (Pl. 6) were found in varying abundances. Additionally, Palythoa mutuki Carlgren (Pl. 7) and Isaurus tuberculatus Gray (Pl. 4) were found in most locations surveyed (10 and 8 sites, respectively – Table 2). Zoanthus kuroshio (Pl. 3 D-E) was only observed at the Nishidomari-Matsubae site in tide pools above the extreme low tide line. Additionally, single colonies of a potentially undescribed species of Isaurus (to be reported elsewhere) (Pl. 5) were observed and sampled from the Shirigai-Matsubae and Nishidomari-Matsubae sites.

Bungo Strait region species diversity

A total of ten sites were investigated in the Bungo Strait region, with a total of five zooxanthellate zoanthid species present (Fig. 1b, Table 2). Two sites were investigated at Okinoshima Island. On the north coast of the island at the Torinokubi site, the species Z. sansibaricus, Z. gigantus, Z. vietnamensis and P. tuberculosa were common, while on the northeast coast at the Oura site, only P. tuberculosa was common, with occasional colonies of Z. gigantus and Z. vietnamensis observed. Four sites were investigated in the Otsuki Town portion of the Bungo Strait, and only three species observed. The Ostuki – Bungo Strait coastline sites are characterized by being much more sheltered from the open ocean than the other sites in this study. Despite numerous dives at the four sites in Ostuki – Bungo Strait, only three zooxanthellate species were confirmed to be present, and all in low abundances; Z. gigantus, Z. vietnamensis, and P. tuberculosa. No zoanthids were observed at the Komo site. Additionally, four sites were investigated in Ehime on the Bungo Strait, and five species of zooxanthellate zoanthids observed. Z. sansibaricus, Z. gigantus, Z. vietnamensis and P. tuberculosa were abundant at the Jinoiso site. At Kashima, Z. vietnamensis was particularly abundant. P. mu tu k i was confirmed only at the Yokoshima site. No zoanthids were observed at the Kurobae site.

Species diversity analyses results

Zooxanthellate zoanthid species numbers at Pacific Coast region sites (average 5.5 ± 0.8, n = 13) were higher than species numbers at non-Pacific Coast region sites (average 2.5 ± 2.2, n = 10). Species numbers of sites with “outside” exposure were also significantly higher (average 5.3 ± 0.9, n = 13) than species numbers at “sheltered” sites (average 2.7 ± 2.1, n = 13). Additionally, the average number of species per site as classified by the three classes of wave and current activity were also different (high 4.9 ± 1.8, n = 13; medium 3.7 ± 2.4, n = 7; low 2.6 ± 1.5, n = 3).

8 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

List of zooxanthellate zoanthids found in southern Shikoku

I. Family Zoanthidae

The family Zoanthidae is the only family within the Order Zoantharia to not be sand-encrusted. All three genera (Zoanthus, Isaurus, Acrozoanthus) in Zoanthidae are zooxanthellate and found worldwide in shallow tropical and sub-tropical waters.

A. Genus Zoanthus

The genus Zoanthus can be distinguished from most other zoanthid genera by its lack of sand and/or detritus uptake. Although Isaurus spp. (also Family Zoanthidae) similarly do not incorporate detritus into their tissue, unlike Isaurus species’ polyps that usually have tubercules Zoanthus polyps are uniformly smooth on the outer surface. Zoanthus spp. can also often be distinguished from the other species and genera observed in this study by often having brightly colored oral disks, although green and brown forms (similar to Palythoa spp.) do exist. The external surface of polyps and the coenenchyme is mainly light to dark purple, although pale green polyp colors are sometimes observed. Zoanthus species are quite common along southern Shikoku shorelines, and are usually found in locations with high wave or current activity and high light levels. All Zoanthus species noted in southern Shikoku are attached to hard substrate, usually large rocks, but also occasionally dead hard corals. Four species have been confirmed to exist in the study area, with three of the species (Z. sansibaricus, Z. gigantus, Z. vietnamensis) quite common. The four species of Zoanthus described here were found from depths ranging from the lower intertidal zone to approximately 5 m.

1. Zoanthus sansibaricus Carlgren, 1900 (Plate 1)

Brief description: As described in Reimer et al. (2006a), Z. sansibaricus often forms large colonies with “liberae” polyps well clear and free of the coenenchyme (see Pax 1910). Adult polyps 3-12 mm in diameter, up to 20 mm in length. External polyp surface light to dark purple, no markings, generally uniform in color, may be slightly paler around edge of oral disk. 40-58 tentacles, 48-54 mesenteries. Wide variation in oral disk color (orange, red, green, brown, purple, white, blue, yellow), often fluorescent. Remarks: Z. sansibaricus has previously been shown using genetic data to consist of many different color morphotypes (Reimer et al. 2004; 2006a), and similar to previous studies here many different color morphotypes (oral disks green, orange, blue, white etc) of Z. sansibaricus were observed. However, compared to Z. gigantus and Z. vietnamensis, Z. sansibaricus appears to be not as common in terms of colony numbers in the area examined here, and much less common than observed at Sakurajima, Kagoshima, Japan (Reimer et al. 2006a; Ono et al. 2007). In all other areas examined in Japan to date (see Fig. 1a), Z. sansibaricus is the most common Zoanthus species. We can offer no explanation for the relative lack of Z. sansibaricus abundance in southern Shikoku, and reasons for this remain to be investigated. As has been previously noted in other Japanese locations (Kagoshima, Wakayama, Hachijojima, REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 9

Miyakejima), Z. sansibaricus is exclusively found below the extreme low tide line. This species appears to have undergone reticulate evolution with another unknown Zoanthus species some time in the past (Reimer et al. 2007).

2. Z. gigantus Reimer & Tsukahara, 2006 (Plate 2)

Brief description: Polyps “liberae” and extend from poorly developed coenenchyme. Often polyps less crowded together than Z. sansibaricus. Polyps up to 25+ mm in diameter, up to 40 mm in length, larger in diameter towards oral opening than at base, appear “swollen” when closed. External surface of polyps purple with white or pale striped vertical markings on upper half. 42-60 tentacles, approximately 62 mesenteries. Oral disk color may vary (orange, red, brown, pink, gray, blue), often with fluorescent green oral opening. Colonies vary widely in size (< 50 polyps to thousands of polyps). Remarks: Z. gigantus was relatively abundant at many sites in this study, particularly along the Pacific coast. In the original description of Z. gigantus, colonies of this species were described as relatively small (< 100 polyps) (Reimer et al. 2006a), but unlike in other areas of Japan examined thus far, often colonies of Z. gigantus along the Pacific coast of Ostuki are very large (thousands of polyps). Additionally, colonies of different color morphotypes were often observed interspersed with each other at sites investigated in this study, a phenomenon seen previously with Z. sansibaricus and also between Z. sansibaricus and Z. vietnamensis (see Fig. 1 in Reimer et al. 2006b), but not previously observed in Z. gigantus. The most commonly observed oral disk color morphotypes of Z. gigantus were orange (Pl. 2 B, C & E) and mint green (Pl. 2 F). Similar to Z. sansibaricus, Z. gigantus is found only below the extreme low tide line in southern Shikoku. Z. gigantus has only recently been described, and no common Japanese name exists for this species. We would like to designate a Japanese name of “budo-mamesunaginchaku” (ブド ウマメスナギンチャク) for Z. gigantus in reference to its large, “swollen” appearance compared to other Zoanthus species in Japan (“budo” means “grape” in Japanese).

3. Z. vietnamensis Pax & Müller, 1957 (Plate 3 A-C)

Brief description: As described in Uchida (2001) and Reimer et al. (2006b), Z. vietnamensis forms small colonies (less than 100 polyps). However, in this study many large colonies (thousands of polyps) were observed. Polyps up to 30 mm in length, up to 20 mm in diameter. Polyps “liberae”. Oral disk always pale to dark pink, often with white oral opening. 55-64 tentacles. Remarks: Z. vietnamensis is the most abundant Zoanthus species in southern Shikoku, often forming large colonies (thousands of polyps) below the extreme low tide line. Like Z. sansibaricus and Z. gigantus, Z. vietnamensis was most common in areas of high wave or current activity, but was also occasionally found in very sheltered areas. For example, a large colony of Z. vietnamensis was found in very sheltered Tachibanaura Harbor surrounded by Acropora colonies. Z. vietnamensis, Z. sansibaricus, and Z. gigantus often occur sympatrically in many sites examined here.

10 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

4. Zoanthus kuroshio Reimer & Ono, 2006 (Plate 3 D & E)

Brief description: Similar to Z. vietnamensis, Z. kuroshio usually with pale pink oral disk, although white and pale blue varieties observed. 42-48 mesenteries, 50-64 tentacles. Polyps “immersae”, deeply embedded, barely extend from coenenchyme. Oral disk 6-12 mm in diameter expanded. Polyps narrower in diameter towards oral opening than at base. Edge of coenenchyme “tongue-like” in form. Colonies often intertidal and in tide pools on wave-exposed shoreline, can be very large and encrusting, forming a “mat” over substrate (rock or dead coral). Remarks: Z. kuroshio was found only at one site examined in this study. Unlike the other three Zoanthus species examined, Z. kuroshio was found above the extreme low tide line, in tidepools facing the ocean at Nishidomari-Matsubae. This is similar to Z. kuroshio as observed on Yakushima (Reimer et al. 2006a). Based on molecular data, there is some question as to whether Z. kuroshio is only a morphotype of Z. vietnamensis (Reimer et al. 2006b), but we have included this species here as its morphology is clear and distinct from Z. vietnamensis and other Zoanthus species. Similar to Z. gigantus, Z. kuroshio has only recently been described, and no common Japanese name exists for this species. We would like to designate a Japanese name of “kuroshio-mamesunaginchaku” (クロシオマメスナギンチャク) for Z. kuroshio in reference to its distribution along the Kuroshio Current in Japan.

B. Genus Isaurus

Isaurus differs from Zoanthus by having recumbent polyps (in daytime) that are generally closed during the daytime, becoming open and upright at night. Additionally, some species or individuals have small, rough tubercules on the exposed upper surface of their polyps. While the genus Isaurus is now well-established, historically there has been some confusion about whether or not this genus is truly separate from Zoanthus (see Muirhead and Ryland [1985] for a description of this), as although Isaurus species are distinguishable from Zoanthus spp. by the morphological traits listed above, other morphological traits (no sand-encrustation, generally colonial, zooxanthellate, “liberae” polyps) as well as their ecology (found in shallow tropical and sub-tropical waters) very closely resemble Zoanthus.

5. Isaurus tuberculatus Gray, 1828 (Plate 4)

Brief description: As described in Uchida (2001) and Muirhead and Ryland (1985), polyps recumbent in daytime, with many tubercules on upward surface of polyps. Some polyps may lack tubercules. Crown tubercules well-formed, clearly delineating oral disk area from capitulum. Body tubercules often in longitudinal series. Tubercules green, white, or gray, sometimes fluorescent. Polyp surface coloration cryptic and varies with environment (white, gray, red, purple), often reflecting surrounding sea weed and corals. Polyps average approximately 2 cm in length, though smaller and larger polyps common. Base of polyps and coenenchyme often with white or pale in color. Colonies small (usually < 50 polyps). Remarks: Until now, Isaurus was known only from a few sites in Japan – including two REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 11 investigated here (Tatsukushi and Nishidomari) as well as the Danjo Islands in Nagasaki, and believed to be very rare. While Isaurus is undoubtedly less frequently encountered than Zoanthus and Palythoa species, this survey reveals I. tuberculatus colonies to be much more common than previously believed, at least along the Pacific Coast of Kochi. We have added six new sites to the known distribution of I. tuberculatus in Japan, and additional data (JDR, not shown) that will be presented elsewhere expands the distribution of I. tuberculatus to the Nansei Islands in Kagoshima. Uchida (2001) lists this Isaurus sp. in Japan as I. assymetricus (originally described from Australia in Haddon and Shackleton [1891]), but the original binomen of this species is I. tuberculatus (Gray 1828, unknown origin) according to Muirhead and Ryland (1985), and we have followed their suggestions in this study. Further studies should clarify the status of Isaurus species diversity. In this study, I. tuberculatus seems to prefer areas of shoreline with large rock walls and high current and wave activity, but not directly exposed to waves, and is often found in the “corners” of small bays behind points and headlands. Often colonies are attached to cracks in large rocks just below the extreme low tide line.

6. Isaurus sp. B undescribed (Plate 5)

Brief description: Unlike I. tuberculatus, colonies large (thousands of polyps), with small green polyps less than half the length (approximately 1 cm) of I. tuberculatus. Tubercules purple, more rounded than I. tuberculatus, and not arranged in the longitudinal fashion as often seen in I. tuberculatus. Base of polyps and coenenchyme often with white or pale in color. Remarks: Only two colonies of this potential new species have been found in the study area; one colony each at Shirigai Matsubae and Nishidomari Matsubae sites. An Isaurus sample from the Danjo Islands (nominally named Isaurus brevia by Uchida, personal communication) appears to have very similar morphology to the two Isaurus sp. B samples from this study. The molecular phylogeny of these samples and I. tuberculatus are currently being investigated and will be presented elsewhere. It remains to be seen whether these samples are conspecific with I. tuberculatus or not, as both Larson and Larson (1982) and Muirhead and Ryland (1985) note that I. tuberculatus has high levels of polyp morphological variation. In this study, the two colonies were both found in shallow water (< 3 m), and similar to I. tuberculatus, in areas with high current but not direct exposure to waves.

II. Family Sphenopidae

This family differs from Zoanthidae in that it is sand-encrusted. Sphenopidae includes the zooxanthellate colonial genus Palythoa with many species worldwide, as well as the solitary zoanthid genus Sphenopus.

A. Palythoa species

Palythoa species (Family Sphenopidae) can be distinguished from the other two zooxanthellate genera present in southern Shikoku by the fact that they take up sand and detritus to help form their structure. Unlike Zoanthus species, Palythoa species of southern 12 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

Shikoku do not have a wide variety of oral disk color variation; usually with either green or brown coloration. Similarly, colony and polyp tissues are usually tan or brown, although patchy bleaching is sometimes observed in larger P. tuberculosa colonies. Palythoa species in southern Shikoku appear to prefer the same general high wave/current, high light levels and hard substrate conditions as Zoanthus and Isaurus, and often occur sympatrically with these two genera.

1. Palythoa tuberculosa Delage & Herouard, 1901 (Plate 6)

Brief description: As described in Uchida (2001) and Reimer et al. (2006c), polyps “immersae”, barely extending above large, well-developed coenenchyme. Oral disks up to 20 mm in diameter, though often closed in day time Coenenchyme white to dark brown, generally uniform in color although some patchiness often observed. Colonies small to large (see remarks below). Like Z. kuroshio, colonies encrust substrate. Remarks: Palythoa tuberculosa was the most common zooxanthellate zoanthid at the sites examined in this study. P. tuberculosa has been previously noted for its ability to exist in environments that are often more “marginal” than many other colonial cnidarians (see Reimer et al. 2006d). At the sites examined here, P. tuberculosa, like most other zooxanthellate zoanthids, was found below the extreme low tide line. However, P. tuberculosa was often found extending to deeper depths than the other zooxanthellate species found in southern Shikoku. An example of this was seen at the Futatsubae site, where P. tuberculosa colonies were noted at depths to 9 m, and no other zoanthids were found at this site. Similarly, P. tuberculosa at Nishidomari has been observed to depths of 8 m (J. Reimer, personal observation) and east of Omurabai at 16 m (J. Reimer, personal observation), as well as in other areas of Japan (Yakushima) as deep as approximately 10 m (Reimer et al. 2006c). P. tuberculosa appears to have at least two major growth forms. One form is a “massive encrusting” colony form, in which a single colony can cover several square meters of hard substrate (Pl. 6 C). Examples of this form were in particular noted at Torinokubi and Tatsukushi-Bentenjima sites. The other, and most common form in southern Shikoku, are “small, rounded” colonies usually no more than 30 cm in diameter (for example, see Pl. 6 F). It remains to be determined if there are any distinctive genetic differences between these two forms.

2. Palythoa mutuki Carlgren, 1937 (Plate 7)

Brief description: As described in Ryland and Lancaster (2003) and Reimer et al. (2006c), polyps “liberae” in form, up to 40 mm in length. Oral disk diameter up to 30 mm, oral disk color green or brown. Radii often visible (white, pale brown). Colonies generally small (<100 polyps). Remarks: In the area investigated in this study, P. m u tu ki, although found at most sites, was only encountered uncommonly, and not with the frequency of P. tuberculosa. Often P. m u tu k i was found on rock walls in areas somewhat shaded, and almost never in areas with very high light levels (on tops of rocks, etc.) that Zoanthus spp. seem to prefer. Previous studies have suggested P. mu tu k i consists of at least two to four clades based on genetic data (Reimer et al. REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 13

2006c), but here we included all P. m u tu k i morphotypes as one species as phylogeny within this “species group” remains to be clarified. P. m u tu k i has been further shown to be closely related to P. tuberculosa, and may have undergone reticulate evolution with P. tuberculosa at some point in the past (Reimer et al., unpublished data).

Morphological dichotomous key to zooxanthellate zoanthids in southern Shikoku.

1. Polyps sand-encrusted – go to 3 and 4. 2. Polyps not sand-encrusted – go to 5 and 6. 3. Polyps barely free of coenenchyme (“immersae”) – Palythoa tuberculosa. 4. Polyps free and clear of coenenchyme (“liberae”) – Palythoa mutuki. 5. Polyps upright – go to 7 and 8. 6. Polyps recumbent – go to 12 and 13. 7. Polyps barely free of coenenchyme (“immersae”) – Zoanthus kuroshio. 8. Polyps free and clear of coenenchyme (“liberae”) – go to 9, 10, and 11. 9. Polyps pale to dark purple, with pale or white oral disk – Zoanthus vietnamensis. 10. Polyps with vertical white or pale stripes on upper half when closed – Zoanthus gigantus. 11. Polyps with no vertical stripes on outside surface, with oral disks not pale to dark purple – Zoanthus sansibaricus. 12. Colonies small (< 50 polyps), polyps up to 2 or 3 cm in length – Isaurus tuberculatus. 13. Colonies large (thousands of polyps), polyps <1.5 cm in length – Isaurus sp. B.

Discussion

While the main purpose of this investigation was to list the species of zooxanthellate zoanthids between Cape Ashizuri and the Yura Peninsula, it became obvious during the course of the survey that the numbers and frequency of species along the Pacific Coast region were higher than at Bungo Strait locations. As shown in our statistical analyses, it appears that zooxanthellate zoanthids prefer locations on the open ocean with high amounts of wave activity and/or current. However, these results must be interpreted with caution. As shown in Table 1, the Pacific Coast region is geographically characterized by a well-developed coastal terrace. On the other hand, the Bungo Strait region has steep underwater cliffs and a dearth of coastal terraces in shallow waters. Thus, the Pacific Coast region’s high zoanthid species diversity and numbers may be not necessarily due to wave and current action, but due to the relatively greater amount of preferable habitat for zooxanthellate zoanthids inherent to the Pacific Coast region. Clearly, investigations over a wider area, including locations on the open ocean with little or no coastal terrace, are necessary to draw conclusions on the environmental factors influencing zooxanthellate zoanthid species diversity. In the future, more surveys and sampling in Ehime Prefecture and on the open ocean side of Okinoshima Island, as well as preliminary surveys northwards along the Pacific Coast of Shikoku should help complete the picture of zooxanthellate zoanthid distribution in Shikoku.

14 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

Acknowledgements

The author would like to thank Fumihito Iwase, Dr. Yoko Nozawa, Shu Nakachi and Kouki Tanaka (all Biological Institute on Kuroshio), Mai Miyamoto and Miho Watanabe (Tokai University), Masao Nakano (Seahorse Diving, Otsuki), Teruo Morita (Pacific Marine Diving, Sukumo), Shinichi Yoshida (Mushadomari Port, Ehime) and Kazutoshi Nishimoto and Atsushi Nishimoto (Tatsukushi Port) for support and guidance during zoanthid surveys. Additionally, Drs. Shusuke Ono (Higashi Miyakonojo High School, Miyazaki) and Junzo Tsukahara (Kagoshima University) lent their support to this study. Mika Reimer assisted with sampling at numerous sites. Dr. Hiro’omi Uchida (Kushimoto Marine Park, Wakayama) is acknowledged for kindly supplying the Isaurus sample from the Danjo Islands.

References

Iwase, F. 2004. Chapter 6 – Shikoku. In Coral Reefs of Japan. Ministry of the Environment, Tokyo, Japan., pp. 258–269. Larson, K.S. and R.J. Larson. 1982. On the ecology of Isaurus duchassaingi (Andres) (: Zoanthidea) from South Water Cay, Belize. In The Atlantic barrier ecosystems at Carrie Bow Cay, Belize, I: Structure and Communities. Rutzler, K. and I.G. MacIntyre (editors). Smith. Cont. Mar. Sci., 12. pp. 475-488. Muirhead, A. and J.S. Ryland. 1985. A review of the genus Isaurus (Zoanthidea) including new records from Fiji. Journal of Natural History, 19: 323-335. Ono, S., J.D. Reimer and J. Tsukahara. 2005. Reproduction of Zoanthus sansibaricus in the infra-littoral zone at Taisho Lava Field, Sakurajima, Kagoshima, Japan. Zool. Sci., 22: 247-255. Ono, S., J.D. Reimer and J. Tsukahara. 2007. Thriving cnidarian community on the volcanic coastline of Sakurajima Taisho Lava Field, southern Japan. Coral Reefs, 26: (in press). Pax, F. 1910. Studien an westindischen Actinien. Zool. Jahrb. Suppl., 11: 157-330. Reimer, J.D., S. Ono, K. Takishita, Y. Fujiwara and J. Tsukahara. 2004. Reconsidering Zoanthus spp. diversity: molecular evidence of conspecifity within four previously presumed species. Zool. Sci., 21: 517-525. Reimer, J.D., S. Ono, A. Iwama, J. Tsukahara, K. Takishita and T. Maruyama. 2006a. Morphological and molecular revision of Zoanthus (Anthozoa: Hexacorallia) from southwestern Japan with description of two new species. Zool. Sci., 23: 261-275. Reimer, J.D., S. Ono, A. Iwama, J. Tsukahara and T. Maruyama. 2006b. High levels of morphological variation despite close genetic relatedness between Zoanthus aff. vietnamensis and Zoanthus kuroshio (Anthozoa: Hexacorallia). Zool. Sci., 23: 755-761. Reimer, J.D., S. Ono, K. Takishita, J. Tsukahara and T. Maruyama. 2006c. Molecular evidence suggesting species in the zoanthid genera Palythoa and Protopalythoa (Anthozoa: Hexacorallia) are congeneric. Zool. Sci., 23: 87-94. Reimer, J.D., K. Takishita and T. Maruyama. 2006d. Molecular identification of symbiotic dinoflagellates (Symbiodinium spp.) from Palythoa spp. (Anthozoa: Hexacorallia) in Japan. Coral Reefs, 25: 521-527. Reimer, J.D., K. Takishita, S. Ono, J. Tsukahara and T. Maruyama. 2007. Molecular evidence REIMER : ZOOXANTHELLATE ZOANTHIDS FROM SOUTHERN SHIKOKU, JAPAN 15

suggesting intraspecific hybridization in Zoanthus (Anthozoa: Hexacorallia). Zool. Sci., 24: (in press). Uchida, H. 2001. Sea Anemones in Japanese Waters. TBS Britannica, Tokyo, Japan, pp. 118-124 (in Japanese).

Explanation of Plates

PLATE 1

Zoanthus sansibaricus Various morphotypes in situ at A) Nishidomari-Matsubae, depth 1 m, B) Jinoiso, 2.5 m, C) Nishidomari, 1.5 m, D) Nishidomari-Matsubae, 0.5 m and E) Nishidomari-Matsubae, 1.5 m, respectively.

PLATE 2

Zoanthus gigantus Various morphotypes in situ at A) Nishidomari-Matsubae, depth 1.5 m, B) Mizushima, 2 m, C) Obae, 1.5 m, D) Nishidomari-Matsubae, 2 m, E) Nishidomari-Matsubae, 2 m and F) Nishidomari-Matsubae, 3.5 m, respectively.

PLATE 3

Zoanthus vietnamensis Various morphotypes in situ at A) Jinoiso, depth 1.5 m, B) Kashima, 0.5 m and C) Yokoshima, 1.5 m, respectively. Zoanthus kuroshio Various morphotypes in situ at D) Sangohama, Kurio, Yakushima, Kagoshima, depth + 0.5 m above extreme low tide line and E) Sangohama, Kurio, Yakushima, Kagoshima, 0 m, respectively. Colonies of Z. kuroshio observed at Nishidomari-Matsubae of very similar form and coloration, but due to their location in tide pools exposed to high wave activity, no in situ images were able to be obtained.

PLATE 4

Isaurus tuberculatus Various morphotypes in situ at A) Hozaki, depth 1.5 m, B) Hozaki, 4 m, C) Hozaki, 1.5 m, D) Mizushima, 0.5 m, E) Mizushima, 0.5 m and F) two polyps from different colonies at Shirigai-Matsubae in a tank at BIK, respectively.

16 Kuroshio Biosphere : BULL. BIOL. INST. KUROSHIO Vol. 3, 2007

PLATE 5

Isaurus sp. B A) and B) colony from Shirigai-Matsubae in situ, depth 2 m. C) and D) polyps from same colony in a tank at BIK. PLATE 6

Palythoa tuberculosa Various morphotypes in situ at A) Shirozaki, depth 1 m, B) Nishidomari South, 0.5 m, C) Torinokubi, 4.5 m, D) Mizushima, 1.5 m, E) Shirozaki, 1 m, F) Shirozaki, 1 m and G) Torinokubi, 3 m, respectively.

PLATE 7

Palythoa mutuki Various morphotypes in situ at A) Odo South, depth 2 m, B) Tatsukushi-Bentenjima, 2 m, C) Nishidomari South, 2 m and D) Tatsukushi-Bentenjima, 0.5 m, respectively.

PLATE 1 A B

1 cm 1 cm

C D

10 cm 1 cm

E

1 cm PLATE 2 A B

C

D

E F PLATE 3 A

1 cm

B C

1 cm 10 cm

D E

1 cm 1 cm PLATE 4 A B

1 cm 1 cm

C D

1 cm

E 1 cm

F

1 cm 1 cm PLATE 5 A B

10 cm

C 1 cm

D

1 cm

1 cm PLATE 6 A B

1 cm

1 cm D

C

1 cm

20 cm F

E

1cm

1 cm G

1 cm PLATE 7 A B

1 cm 1 cm

C D

1 cm 1 cm